In the field of helicopter construction, the main rotor and tail rotor are usually driven by means of a helicopter rotor transmission, usually in the form of a planetary transmission. Such a helicopter transmission is housed in a transmission housing. The transmission housing is attached to the load-bearing structure of the helicopter at a plurality of points and is coupled to a rotor. This type of helicopter rotor transmission has prevailed, since a compact, extremely reliable and weight-saving design is possible.
Planetary transmissions are of known art, and when used as helicopter rotor transmissions these planetary transmissions have a plurality of externally toothed planetary gears, which are mounted on associated planetary carriers. As dictated by the design the planetary gears are mounted in a locationally fixed gear ring, in the form of an internally toothed ring gear, such that they can rotate about themselves and within the ring gear. In this case, the planetary gears respectively rotate about their planetary axes and rotate within the gear ring about a central rotor axis. The rotation of the planetary gears is effected by a rotational drive of a central sun wheel, which is also locationally fixed, but is mounted such that it can rotate about the central rotor axis. A drive rotates the central sun wheel so that the rotational movement is transferred via the sun wheel and the planetary gears onto the rotor mast, wherein the rotor mast protrudes from the side of the transmission housing remote from the drive side. With this arrangement of known art, compact, light, sufficiently powerful and robust helicopter rotor transmissions can be achieved so as to drive various rotor masts.
In practice, however, it has been shown that this type of helicopter rotor transmission requires increased maintenance costs. In particular, the lubrication system must be checked and readjusted sufficiently frequently. Since as much weight as possible must be saved in helicopter construction, additional devices for an automatic lubrication system, for the control of an automatic lubrication system, or for the complex return and reuse of lubricant are omitted as far as possible. Accordingly, the moving components must be checked for sufficient lubrication at regular intervals and manually readjusted. Up to the present time the helicopter rotor transmissions of known art must be serviced and/or repaired once more after just a few flying hours, as dictated by circumstances and costs.
The lubrication systems of helicopter rotor transmissions of known art have already been optimised by the use of different lubricants, wherein semi-automatic single lubrication procedures have also been investigated. An attempt has also been made to reduce maintenance costs by means of a central lubrication system. However, none of these efforts have as yet led to the desired significant reduction in maintenance costs for such helicopter rotor transmissions. There is a desire to simplify the lubrication system of the helicopter rotor transmission, which is not easy because of the poor access to the helicopter rotor transmission.